First ever image of a black hole: A CNRS researcher had simulated it as early as 1979

The first real image of a black hole, obtained by the international network of EHT telescopes and published on April 10, 2019 in Astrophysical Journal Letters1, shows the extraordinary accuracy of the world’s very first simulation of a black hole 40 years earlier by Jean-Pierre Luminet, then a young researcher at the CNRS.

Published in 1979 in Astronomy and Astrophysics2, it had a worldwide impact, especially since this type of object was still highly theoretical. It is not an artist’s view but an image based on the then supposed physical properties of a black hole and its gas disc, such as its rotation rate and temperature, and on Einstein’s general theory of relativity.

Luminet envisioned it as a black circle, which had not yet become known as the shadow of the black hole, in the centre of a luminous accretion disc, with one side clearly brighter than the other. This is because there are two effects that should shift the radiation that reaches us from the disc: the Einstein effect, in which the gravitational field reduces its frequency and decreases its intensity, and the Doppler effect, in which the displacement of the source in relation to the observer produces an increase in frequency when the source approaches and a decrease when it moves away: an effect caused by the rotation of the accretion disc around the black hole.

These are all characteristics that can be found in the real image obtained forty years later by the EHT, which shows just how accurate this first simulation was.

Jean-Pierre Luminet is currently a CNRS Emeritus Senior Researcher at the Laboratoire d’Astrophysique de Marseille (CNRS/CNES/Aix-Marseille Université) and associated with the Luth (Observatoire de Paris/CNRS).

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